Czech Republic, meanwhile, snatched a 2-2 draw against Croatia on matchday two, a result that means they could still go through in second place should leaders Spain beat Ante Cacic's side.
Reports of unrest within the squad and some heavy criticism of star midfielder Arda Turan has cast a shadow over Turkey's preparations, but Cech expects them to provide a stern test in what he considers to be their biggest game so far.
"The most important thing is how we play," said the Arsenal goalkeeper. "Their game will be different, they'll make it difficult but we have to prepare ourselves for our best performance. It's the most important match in the group and that's what we're focused on.
"I think they're a good team, a quality team. They lost the first matches, we lost the first and almost the second, but we can still say they defeated us 2-0 in Prague. They're still fighting for their chance to qualify. We're not looking at their two matches. They'll be extra motivated and they'll want to show themselves.
"They have quality midfield players. I don't want to pick only one because there might be some changes but we're trying to prepare ourselves for all eventualities."
Turkey came from 2-0 down to beat the Czechs 3-2 at Euro 2008, but Cech says any notion of revenge will be centred around the qualifiers for these finals, when each side beat the other away from home.
"This will mainly be a revenge for the match in Prague where we lost in qualifiers," he said. "It was different eight years ago, the players aren't the same, we can't compare these two matches.
"The most important thing is to find a style that will bring us success. But the maths is clear: if we want to go through and not wait on other teams, we have to win."
Veteran midfielder Tomas Rosicky will miss the game with a thigh injury, but Cech is confident that his side have the quality and the fan backing to overcome his absence.
"He's a big loss, he's one of the key players but the others will have to step up," he said. "We are a team whose biggest strength is the team play, we don't have big stars. Our togetherness is a big strength. The other players will have a chance to show they can do it.
"We will depend on the support of our fans, we had great attendance, but this is the decisive match so the fans will be most important."